JPWO2015189888A1 - Gas sensor and sensor device - Google Patents

Abstract

A solid electrolyte layer containing positive charge carriers for coordinating the gas to be detected; an electrode disposed on a part of one surface of the solid electrolyte layer; and means for promoting the movement of the positive charge carriers. It is a gas sensor.

Description

  The present disclosure relates to a gas sensor and a sensor device including the gas sensor.

Conventionally, as a gas sensor for detecting a gas such as ammonia or nitrogen oxide, a gas sensor for detecting a gas based on a change in electric resistance has been used. The gas sensor detects the gas based on a change in electrical resistance of the semiconductor caused by adsorption of the gas on the surface of a semiconductor such as tin dioxide.
In the gas sensor that detects gas based on a change in electric resistance, it is necessary to supply a current to the semiconductor using a constant current power source in order to measure the changing electric resistance. Therefore, the gas sensor that detects gas based on a change in electrical resistance has a problem that power consumption of the detection circuit itself increases.
In the gas sensor, it is necessary to heat the semiconductor to a temperature (for example, 400 ° C.) at which good detection characteristics can be obtained. Therefore, the gas sensor has a problem that a large amount of electric power must be used for a heater for heating the gas sensor.

In view of this, a gas sensor has been proposed that detects a gas based on a change in potential difference caused by adsorption of the gas, not a change in electrical resistance. As said gas sensor, the gas sensor using the solid electrolyte which has ion conductivity, such as oxygen ion conductivity, oxide ion conductivity, proton conductivity, is proposed, for example (for example, refer patent documents 1-4). ).
However, in these proposed techniques, the temperature at which the solid electrolyte (for example, zirconia) used exhibits good ion conductivity is a high temperature of 300 ° C. or higher. Further, in these proposed techniques, in order to cause a change in potential difference in the solid electrolyte, a chemical reaction such as an oxidation reaction of an adsorbed gas is used, so that the gas sensor is heated to a temperature at which the chemical reaction occurs. There is a need.
Therefore, in these proposed techniques, there is a problem that a large amount of electric power must be used for a heater for heating the gas sensor.

Further, as a gas sensor for detecting gas at room temperature, a gas sensor using a CuBr film that can detect NH ₃ gas at room temperature with high sensitivity and high selectivity has been proposed (see, for example, Non-Patent Document 1). ). In the proposed technique, gas is detected based on a change in electrical resistance. Therefore, in order to measure a change in electrical resistance, it is necessary to supply a current to the CuBr film using a constant current power source, which causes a problem that power consumption of the detection circuit itself increases.

  Therefore, at present, there is a need to provide a gas sensor that does not need to be supplied with a current using a constant current power source and that does not require heating and can be used with low power consumption, and a sensor device including the gas sensor. is there.

JP 2002-031619 A JP 2005-221428 A JP 2007-248335 A JP 2009-198346 A

Pascal Lauque, Marc Bendahan, Jean-Luc Seguin, Kieu An Ngo, Philippe Knauth, Analytical Chima Acta, 515, 279, (284)

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, this case does not require the supply of current using a constant current power supply, and does not require heating, and can be used for power saving, and a sensor device that can be used for power saving without heating. The purpose is to provide.

Means for solving the problems are as follows. That is,
The first aspect of the disclosed gas sensor comprises:
A solid electrolyte layer containing positive charge carriers for coordinating the gas to be detected;
A first electrode disposed on a part of one surface of the solid electrolyte layer;
On the other surface of the solid electrolyte layer, there is a second electrode arranged opposite to the first electrode and disposed at a portion other than the portion in contact with the detection target gas.

A second aspect of the disclosed gas sensor comprises:
A solid electrolyte layer containing positive charge carriers for coordinating the gas to be detected;
A first electrode and a second electrode disposed on a surface opposite to the side in contact with the detection target gas in the solid electrolyte layer;
Means for accelerating the movement of the positive charge carriers in the surface direction of the solid electrolyte layer and in the direction from the second electrode to the first electrode in the solid electrolyte layer.

The disclosed sensor device is
The disclosed gas sensor;
Means for detecting a change in potential difference of the gas sensor, connected to the first electrode of the gas sensor.

According to the disclosed gas sensor, it is possible to solve the above-mentioned conventional problems, and to provide a gas sensor that can be used with low power consumption without the need of supplying a current using a constant current power source and heating. it can.
According to the disclosed sensor device, the conventional problems can be solved, and a sensor device that can be used with low power consumption without heating is provided.

FIG. 1A is a schematic cross-sectional view of an example of the first aspect of the disclosed gas sensor. FIG. 1B is a schematic diagram of one surface of an example in the first aspect of the disclosed gas sensor. FIG. 1C is a schematic diagram of the other surface of an example in the first aspect of the disclosed gas sensor. FIG. 2 is a schematic cross-sectional view of another example of the first aspect of the disclosed gas sensor. FIG. 3 is a schematic cross-sectional view of an example in the second aspect of the disclosed gas sensor. FIG. 4A is a schematic cross-sectional view of another example of the second aspect of the disclosed gas sensor. FIG. 4B is a schematic view of one surface of another example of the second aspect of the disclosed gas sensor. FIG. 4C is a schematic diagram of the other surface of another example in the second aspect of the disclosed gas sensor. FIG. 5 is a schematic cross-sectional view of an example of the disclosed sensor device. 6A is a schematic cross-sectional view of the gas sensor of Example 1. FIG. 6B is a schematic diagram of one surface of the gas sensor of Example 1. FIG. 6C is a schematic diagram of the other surface of the gas sensor of Example 1. FIG. FIG. 7 is a graph showing the results of measuring the potential difference of the gas sensor of Example 1. FIG. 8A is a schematic cross-sectional view of the gas sensor of Example 2. FIG. 8B is a schematic diagram of one surface of the gas sensor according to the second embodiment. FIG. 8C is a schematic diagram of the other surface of the gas sensor according to the second embodiment. FIG. 9 is a graph showing the results of measuring the potential difference of the gas sensor of Example 2. FIG. 10 is a schematic cross-sectional view of the gas sensor according to the third embodiment. FIG. 11 is a graph showing the results of measuring the potential difference of the gas sensor of Example 3. FIG. 12A is a schematic cross-sectional view of the gas sensor of Example 4. 12B is a schematic view of one surface of the gas sensor of Example 4. FIG. 12C is a schematic diagram of the other surface of the gas sensor of Example 4. FIG. FIG. 13 is a graph showing the results of measuring the potential difference of the gas sensor of Example 4. 14A is a schematic cross-sectional view of a gas sensor of Comparative Example 1. FIG. 14B is a schematic diagram of one surface of the gas sensor of Comparative Example 1. FIG. 14C is a schematic view of the other surface of the gas sensor of Comparative Example 1. FIG. FIG. 15 is a graph showing the results of measuring the potential difference of the gas sensor of Comparative Example 1.

(Gas sensor)
<First aspect>
The first aspect of the disclosed gas sensor includes at least a solid electrolyte layer, a first electrode, and a second electrode, and further includes other means as necessary.

<< Solid electrolyte layer >>
The solid electrolyte layer is not particularly limited as long as it is a solid electrolyte layer containing a positive charge carrier that coordinates the detection target gas, and can be appropriately selected according to the purpose.
The positive charge carriers are preferably movable at room temperature.
Here, “normal temperature” means a temperature at which the gas sensor is not heated, and is, for example, 25 ° C.
“Moveable” means that the positive charge carriers can move to such an extent that a change in potential difference can be confirmed in the gas sensor.

  The detection target gas is not particularly limited as long as it is a gas that can be coordinated to the positive charge carrier, and can be appropriately selected according to the purpose. Examples of the gas capable of coordinating with the positive charge carrier include nitrogen-containing compounds, oxygen-containing compounds, and sulfur-containing compounds. Examples of the nitrogen-containing compound include ammonia, amine, and nitric oxide. Examples of the sulfur-containing compound include hydrogen sulfide and sulfur dioxide.

  The positive charge carrier is not particularly limited as long as it is a carrier that coordinates the detection target gas, and can be appropriately selected according to the purpose. However, copper ions and silver ions are excellent in terms of carrier mobility. At least one of these is preferable.

The material of the solid electrolyte layer is not particularly limited and may be appropriately selected depending on the purpose, for example, cuprous bromide (CuBr), cuprous sulfide (Cu 2 _S), silver sulfide (Ag ₂ S), silver iodide (AgI), silver rubidium iodide (RbAg ₄ I ₅ ) and the like. Since these solid electrolytes have sufficient positive charge carrier mobility even at room temperature (for example, 25 ° C.), they can be used for the solid electrolyte layer. Among these, cuprous bromide is preferable in that it has excellent mobility of positive charge carriers at room temperature.
There is no restriction | limiting in particular as a shape, a magnitude | size, and a structure of the said solid electrolyte layer, According to the objective, it can select suitably.

  There is no restriction | limiting in particular as a formation method of the said solid electrolyte layer, According to the objective, it can select suitably, For example, sputtering method etc. are mentioned. Moreover, when the material of the said solid electrolyte layer is cuprous bromide, the method of immersing copper in cupric bromide aqueous solution and changing the said copper to cuprous bromide etc. is mentioned.

<< first electrode >>
The first electrode is not particularly limited as long as it is an electrode disposed on a part of one surface of the solid electrolyte layer, and can be appropriately selected according to the purpose.
Examples of the material of the first electrode include a metal that is nobler than the metal element of the positive charge carrier.
Moreover, it is preferable that the material of the first electrode is the same metal as the metal element of the positive charge carrier from the viewpoint that the potential of the solid electrolyte layer becomes stable. In the case where the first electrode has a laminated structure, it is preferable that the material of the electrode in contact with the solid electrolyte layer is the same metal as the metal element of the positive charge carrier.
There is no restriction | limiting in particular as a shape, a magnitude | size, and a structure of a said 1st electrode, According to the objective, it can select suitably.
There is no restriction | limiting in particular as average thickness of a said 1st electrode, Although it can select suitably according to the objective, Less than the average thickness of the said solid electrolyte layer is preferable.

  There is no restriction | limiting in particular as a formation method of a said 1st electrode, According to the objective, it can select suitably, For example, a vacuum evaporation method etc. are mentioned.

<< second electrode >>
The second electrode is an electrode disposed on at least a part of the other surface of the solid electrolyte layer other than a part facing the first electrode and in contact with the detection target gas. There is no restriction | limiting in particular, According to the objective, it can select suitably.
Examples of the material of the second electrode include a metal that is nobler than the metal element of the positive charge carrier.
In addition, it is preferable that the material of the second electrode is the same metal as the metal element of the positive charge carrier from the viewpoint that the potential of the solid electrolyte layer becomes stable. When the second electrode has a laminated structure, it is preferable that the material of the electrode in contact with the solid electrolyte layer is the same metal as the metal element of the positive charge carrier.
There is no restriction | limiting in particular as a shape, a magnitude | size, and a structure of a said 2nd electrode, According to the objective, it can select suitably.

  There is no restriction | limiting in particular as a formation method of a said 2nd electrode, According to the objective, it can select suitably, For example, a vacuum evaporation method etc. are mentioned.

<< Other means >>
There is no restriction | limiting in particular as said other means, According to the objective, it can select suitably, For example, the means etc. which promote the movement of a positive charge carrier are mentioned.

-Means for promoting the movement of positive charge carriers-
As means for promoting the movement of the positive charge carriers, for example, on the other surface of the solid electrolyte layer, the first electrode is opposed to the first electrode and the detection target gas is arranged in contact with the positive electrode. Examples thereof include a layer containing a substance capable of coordinating with positive charge carriers and transmitting the detection target gas. By providing the gas sensor with means for promoting the movement of the positive charge carriers, the movement of the positive charge carriers in the solid electrolyte layer is promoted, and the change in potential difference can be increased.

The layer containing a substance capable of coordinating with the positive charge carrier and transmitting the detection target gas transmits the detection target gas, and therefore the coordination of the detection target gas to the positive charge carrier of the solid electrolyte layer. Does not disturb.
Examples of the substance capable of coordinating with the positive charge carrier include an organic substance having a carbon-carbon double bond. Examples of the organic substance having a carbon-carbon double bond include synthetic rubbers such as natural rubber (polyisoprene), polyisoprene, and polybutadiene, unsaturated fatty acids, unsaturated fatty acid esters, and unsaturated fatty acid amides. Examples of the unsaturated fatty acid include oleic acid and linoleic acid.
The carbon-carbon double bond has the ability to form a coordination bond by donating electrons to atoms and ions of the transition metal. Therefore, the organic substance can dope electrons to the solid electrolyte layer by coordinating with the positive charge carriers. As a result, a bias voltage can be introduced into the solid electrolyte layer, and the movement of the positive charge carriers is promoted.

Here, the 1st aspect of the said gas sensor is demonstrated using figures. A gas sensor when the material of the solid electrolyte layer is cuprous bromide and the detection target gas is ammonia will be described.
The gas sensor shown in FIGS. 1A to 1C includes a solid electrolyte layer 1 made of cuprous bromide, a first electrode 2 that is a gold electrode, and a second electrode layer 3 that is a copper electrode. The first electrode 2 is disposed on a part of one surface of the solid electrolyte layer 1. The second electrode 3 is disposed on the other surface of the solid electrolyte layer 1 other than the gas contact portion 4 facing the first electrode 2 and in contact with the detection target gas.

Ammonia is adsorbed on the gas contact portion 4 which is the surface of the solid electrolyte layer 1. Then, the ammonia is coordinated to the copper ions located in the gas contact portion 4. Since the copper ions coordinated with the ammonia are fixed to the gas contact portion 4 of the solid electrolyte layer 1, they do not function as positive charge carriers. If it does so, in the solid electrolyte layer 1 (area | region (alpha) in FIG. 1A) between the gas contact part 4 and the electrode 2 which opposes the gas contact part 4, a positive charge carrier density | concentration will fall.
On the other hand, in the region β having the surface covered with the second electrode 3, the decrease in the positive charge carrier concentration due to the gas contact does not occur.
Therefore, a state in which the positive charge carrier concentration is different between the region α in the solid electrolyte layer 1 and the region β occurs. Then, the positive charge carriers spontaneously move from the region β to the region α so as to make the concentration inside the solid electrolyte layer 1 uniform. As a result, the potential difference changes inside the solid electrolyte layer 1.

  Since the number per surface area of the copper ions fixed to the gas contact portion 4 is determined by the adsorption equilibrium of ammonia in the gas contact portion 4, the copper ions fixed to the gas contact portion 4 when the ammonia concentration is low. The number per surface area is proportional to the ammonia concentration in the atmosphere. Therefore, the number of copper ions moving from the region β to the region α in order to make the concentration of positive charge carriers uniform, and the potential difference generated thereby are proportional to the ammonia concentration. Therefore, the concentration of the detection target gas can be measured by measuring the potential difference between the first electrode 2 and the second electrode 3.

Next, another example of the first aspect of the gas sensor will be described.
FIG. 2 is a schematic cross-sectional view of another example of the first aspect of the gas sensor.
In the gas sensor of FIG. 2, a natural rubber layer 5 is disposed at a gas contact portion of the solid electrolyte layer 1 as a means for promoting the movement of positive charge carriers. Other configurations are the same as those of the gas sensor of FIGS. 1A to 1C. The natural rubber layer 5 is thin, and the natural rubber layer 5 can transmit the detection target gas.

  In the gas sensor of FIG. 2, the carbon-carbon double bond of the natural rubber layer 5 can dope electrons into the solid electrolyte layer 1, whereby a bias voltage can be introduced into the solid electrolyte layer 1. The movement of positive charge carriers is promoted.

<Second aspect>
A second aspect of the disclosed gas sensor has at least a solid electrolyte layer, a first electrode, a second electrode, and a means for promoting the movement of positive charge carriers, and, if necessary, other It has the means.

<< Solid electrolyte layer >>
The solid electrolyte layer is not particularly limited as long as it is a solid electrolyte layer containing a positive charge carrier that coordinates the detection target gas, and can be appropriately selected according to the purpose. Examples thereof include the solid electrolyte layer exemplified in the first embodiment. The preferred embodiment of the solid electrolyte layer is also the same as the preferred embodiment of the solid electrolyte layer exemplified in the first embodiment of the gas sensor.

  The gas to be detected is not particularly limited as long as it is a gas that can be coordinated to the positive charge carrier, and can be appropriately selected according to the purpose. For example, the nitrogen-containing compound, the oxygen-containing compound, and the sulfur-containing compound Etc. Examples of the nitrogen-containing compound include ammonia, amine, and nitric oxide. Examples of the sulfur-containing compound include hydrogen sulfide and sulfur dioxide.

<< first electrode and second electrode >>
The first electrode and the second electrode are not particularly limited as long as they are electrodes disposed on the surface of the solid electrolyte layer opposite to the side in contact with the detection target gas. For example, the first electrode and the second electrode exemplified in the first aspect of the gas sensor can be used. The preferred embodiments of the first electrode and the second electrode are also the same as the preferred embodiments of the first electrode and the second electrode exemplified in the first embodiment of the gas sensor. .

<< Means for promoting the movement of positive charge carriers >>
As means for promoting the movement of the positive charge carriers, the movement of the positive charge carriers in the surface direction of the solid electrolyte layer and in the direction from the second electrode to the first electrode in the solid electrolyte layer is performed. There is no particular limitation as long as it is a means for promoting, and it can be appropriately selected according to the purpose. However, a voltage source is preferable in terms of simple apparatus configuration, and the detection in the solid electrolyte layer is preferable in terms of power saving. A layer that is disposed on at least a part of the surface on the side in contact with the target gas and covers the solid electrolyte layer is preferable.

-Voltage source-
The voltage source is not particularly limited as long as it is a power source capable of applying a bias voltage in the surface direction of the solid electrolyte layer and in the direction from the second electrode to the first electrode in the solid electrolyte layer. Can be appropriately selected according to the purpose.
By applying a bias voltage in the direction of the solid electrolyte layer using the voltage source, the surface of the solid electrolyte layer on which the detection target gas comes into contact is contacted with the detection target gas. The movement of positive charge carriers is promoted, and the potential difference between the first electrode and the second electrode changes.

-Layer covering the solid electrolyte layer-
The layer covering the solid electrolyte layer is not particularly limited as long as it is disposed on at least a part of the surface of the solid electrolyte layer on the side in contact with the detection target gas and covers the solid electrolyte layer. The positive charge carriers move within the solid electrolyte layer, but can be appropriately selected according to the purpose, and the layer contains a substance capable of coordinating with the positive charge carriers and is permeable to the detection target gas. Is preferable in that it is further promoted.

The layer containing a substance capable of coordinating with the positive charge carrier and transmitting the detection target gas transmits the detection target gas, and therefore the coordination of the detection target gas to the positive charge carrier of the solid electrolyte layer. Does not disturb.
Examples of the substance capable of coordinating with the positive charge carrier include an organic substance having a carbon-carbon double bond. Examples of the organic substance having a carbon-carbon double bond include natural rubber (polyisoprene), synthetic polyisoprene, polybutadiene, unsaturated fatty acid, unsaturated fatty acid ester, and unsaturated fatty acid amide. Examples of the unsaturated fatty acid include oleic acid and linoleic acid.
The carbon-carbon double bond has the ability to form a coordination bond by donating electrons to atoms and ions of the transition metal. Therefore, the organic substance can dope electrons to the solid electrolyte layer by coordinating with the positive charge carriers. As a result, a bias voltage can be introduced into the solid electrolyte layer, and the movement of the positive charge carriers is promoted.

  The thickness or density of the layer covering the solid electrolyte layer is changing from one electrode toward the other electrode on the surface of the solid electrolyte layer on the side where the detection target gas contacts. preferable. The change in the thickness or the density may be a step change or a gradual change. In the gas sensor, when the first electrode is used as a detection electrode and the second electrode is used as a reference electrode, the thickness or density of the layer covering the solid electrolyte layer is a portion facing the first electrode. It is preferable that the portion facing the second electrode is thicker or denser. By doing so, the movement of the positive charge carriers is further promoted.

Here, the 2nd aspect of the said gas sensor is demonstrated using figures. A gas sensor when the material of the solid electrolyte layer is cuprous bromide and the detection target gas is ammonia will be described.
FIG. 3 is a schematic cross-sectional view of an example of the second aspect of the gas sensor. The means for promoting the movement of the positive charge carriers in the gas sensor shown in FIG. 3 is a voltage source.
The gas sensor shown in FIG. 3 has a solid electrolyte layer 11 made of cuprous bromide, a first electrode 12, a second electrode 13, and a voltage source 14. The first electrode 12 and the second electrode 13 are arranged with a gap on a part of the surface of the solid electrolyte layer 11 on the side opposite to the surface with which the gas to be detected contacts. The voltage source 14 has a structure in which a copper electrode 15, a solid electrolyte layer 16, and a silver electrode 17 are laminated in this order.

  Ammonia is adsorbed on the surface of the solid electrolyte layer 11. Then, the ammonia is coordinated to copper ions located on the surface of the solid electrolyte layer 11. Since the copper ions coordinated with the ammonia are fixed on the surface of the solid electrolyte layer 11, they do not function as positive charge carriers. Then, the positive charge carrier concentration is lowered inside the solid electrolyte layer 11. At this time, when a bias voltage is applied to the solid electrolyte layer 11 from the voltage source 14 via the second electrode 13 in contact with the solid electrolyte layer 11, the second electrode 13 having a positive potential can be further Copper ions easily move near the first electrode 12 having a low potential. As a result of the movement of the copper ions, the potential difference between the two electrodes changes.

  This change in potential difference depends on the applied bias voltage and the positive charge carrier density inside the solid electrolyte layer (that is, the amount per surface area of copper ions fixed to the surface of the solid electrolyte layer by ammonia). Therefore, if the bias voltage is made constant, a potential difference corresponding to the ammonia concentration in the atmosphere is generated. Therefore, the gas concentration to be detected is measured by measuring the potential difference between the electrode connected to the voltage source and the other electrode, or the potential difference in the path from the other electrode to the voltage source. can do.

Next, another example of the second aspect of the gas sensor will be described.
4A to 4C are schematic views of other examples in the second mode of the gas sensor.
The gas sensor shown in FIGS. 4A to 4C includes a solid electrolyte layer 21 made of cuprous bromide, a first electrode 22, a second electrode 23, and a layer 24 covering the solid electrolyte layer. Yes. The first electrode 22 and the second electrode 23 are arranged with a gap on a part of the surface of the solid electrolyte layer 11 on the side opposite to the surface with which the detection target gas contacts. The layer 24 covering the solid electrolyte layer is made of natural rubber, and the portion facing the second electrode 23 is more natural per surface area of the solid electrolyte layer 21 than the portion facing the first electrode 22. The amount of rubber is increasing. The change in quantity is gradual. In FIG. 4A and FIG. 4C, the change in the amount of natural rubber is shown in shades of color for easy visual recognition. The darker the color, the greater the amount of natural rubber.

  In the gas sensor of FIGS. 4A to 4C, the portion of the layer 24 that covers the solid electrolyte layer that faces the second electrode 23 is more in the solid electrolyte layer 21 than the portion that faces the first electrode 22. Since the amount of natural rubber per surface area is large, the amount of doped electrons is larger on the second electrode 23 side of the solid electrolyte layer 21 than on the first electrode 22 side. The potential of the first electrode 22 becomes higher than the potential of the second electrode 23 due to the difference in the amount of doped electrons. Furthermore, when the detection target gas contacts the solid electrolyte layer 21, the first electrode in which the amount of natural rubber per area covering the solid electrolyte layer 21 in the solid electrolyte layer 21 is smaller than that in the second electrode 23. In the region close to 22, more detection target gas is fixed. In the solid electrolyte layer 21, in a region away from the layer 24 covering the solid electrolyte layer, the first electrode 22 side is more deficient in positive charge carriers than the second electrode 23 side. In the solid electrolyte layer 21, positive charge carriers diffuse from the second electrode 23 side toward the first electrode 22 side so that the carrier concentration approaches a uniform state. As a result, the potential on the first electrode 22 side becomes higher than the potential of the second electrode 23.

  4A to 4C show an embodiment in which the amount of natural rubber per surface area of the solid electrolyte layer 21 in the layer 24 covering the solid electrolyte layer is gradually changed. However, the embodiment of the layer 24 covering the solid electrolyte layer is shown. Is not limited thereto, and may be a stepwise change in the amount. Further, the layer 24 covering the solid electrolyte layer may be formed only on a part of the surface of the solid electrolyte layer in contact with the detection target gas as long as the movement of positive charge carriers can be promoted.

(Sensor device)
The disclosed sensor device includes at least the disclosed gas sensor and means for detecting a change in potential difference of the gas sensor, and further includes other means as necessary.

<Means for detecting change in potential difference of gas sensor>
The means for detecting the change in the potential difference of the gas sensor is not particularly limited and can be appropriately selected according to the purpose. However, the electric field is different in that the sensor device can be miniaturized and the potential difference change can be amplified. Effect transistors are preferred.

  The means for detecting a change in potential difference of the gas sensor is connected to the first electrode of the gas sensor.

<< Field-effect transistor >>
The field effect transistor is not particularly limited and may be appropriately selected depending on the purpose. For example, the gate electrode for applying a gate voltage, the source electrode and the drain electrode for extracting current, Examples include a field effect transistor having an active layer disposed between a source electrode and the drain electrode, and a gate insulating layer disposed between the gate electrode and the active layer. Examples of the material of the active layer include silicon and metal oxide semiconductors.
The first electrode of the gas sensor is connected to the gate electrode.

Here, an example of the disclosed sensor device will be described with reference to the drawings.
FIG. 5 is a schematic cross-sectional view of an example of the sensor device.
The sensor device shown in FIG. 5 includes a gas sensor and a field effect transistor. The gas sensor includes a solid electrolyte layer 1, a first electrode 2, and a second electrode 3. The first electrode 2 is disposed on a part of one surface of the solid electrolyte layer 1. The second electrode 3 is disposed on the other surface of the solid electrolyte layer 1 other than the gas contact portion 4 facing the first electrode 2 and in contact with the detection target gas. The field effect transistor includes a silicon substrate 51 that also serves as an active layer, a source electrode 52, a drain electrode 53, a gate insulating layer 54, and a gate electrode 55. The gate electrode 52 and the drain electrode 53 are arranged with the active layer interposed therebetween. The gate insulating layer 54 is disposed between the active layer and the gate electrode 55. The first electrode 2 of the gas sensor and the gate electrode 55 of the field effect transistor are connected via a first wiring 56 and a second wiring 57. An insulating layer 58 is formed so as to cover the gate insulating layer 54, the gate electrode 55, the first wiring 56, and the second wiring 57, and the gas sensor is disposed thereon.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
A gas sensor as shown in FIGS. 6A to 6C was produced. Specifically, the gas sensor was produced by the following method.

<Formation of first electrode>
A gold electrode (first electrode 2) having a width of 10 mm, a length of 25 mm, and an average thickness of 30 nm is vacuumed on a silicon wafer with a thermal oxide film having a width of 12 mm × length of 50 mm × thickness of 0.6 mm and an average thickness of 1 μm. It formed using the vapor deposition method.

<Formation of solid electrolyte layer>
A copper layer having a width of 8 mm, a length of 30 mm, and an average thickness of 0.5 μm was formed using a vacuum deposition method so as to cover a part of the first electrode 2. Subsequently, in literature (Pascal Laquee, Marc Bendahan, Jean-Luc Seguin, Kieu An Ngo, Philippe Knauth, Analytica Chimica Acta, ent. By the method, the copper in the said copper layer was changed into cuprous bromide using the cupric bromide aqueous solution, and the solid electrolyte layer 1 was obtained. The average thickness of the obtained solid electrolyte layer was 0.5 μm.

<Formation of second electrode>
Further, as shown in FIG. 6A, a copper layer having a width of 10 mm × a length of 25 mm × an average thickness of 60 nm was formed by vacuum deposition so that the width of the gap G with the first electrode 2 was 1 mm. A gold layer having an average thickness of 30 nm was formed thereon using a vacuum vapor deposition method to obtain a laminated structure (second electrode 3) of a copper layer and a gold layer. Thus, a gas sensor was obtained.
Here, the gap G is the projected first when the first electrode 2 is projected onto the other surface opposite to one surface of the solid electrolyte layer 1 on which the first electrode 2 is disposed. It means the interval between the end portions of the electrode 2 and the second electrode 3 facing each other.

<Evaluation of potential difference change>
A configuration in which a 196 system DMM manufactured by Keithley is connected to the manufactured gas sensor so that the first electrode 2 serves as a detection electrode and the second electrode 3 serves as a reference electrode, and a potential difference between both electrodes is measured. did. The gas sensor was installed in a nitrogen gas flow channel, and the gas source was switched between high-purity nitrogen gas and nitrogen gas containing ammonia having a concentration of 1 ppm to evaluate the reaction of the gas sensor to ammonia. The reaction of the gas sensor was evaluated at room temperature without heating the gas sensor.
High purity nitrogen gas was used at a flow rate of 4.0 L / min. Nitrogen gas containing ammonia with a concentration of 1 ppm was generated by using a permeator (trade name: PD-1B, manufactured by Gastec Co., Ltd.) and generated under the conditions of a temperature of 30 ° C. and a flow rate of 2.8 L / min. .

  FIG. 7 shows the relationship between the measured potential difference and the change with time. Even when the high purity nitrogen gas is in contact with the solid electrolyte layer 1, the potential of the reference electrode is higher than that of the detection electrode due to the equilibrium of the copper redox reaction occurring at the interface between the cuprous bromide and the copper electrode surface. It was as high as 56 mV. When the air flow was switched from high-purity nitrogen gas to nitrogen gas containing ammonia at a concentration of 1 ppm, the potential of the sensing electrode increased, and as a result, the measured potential difference was reduced by about 6 mV. Therefore, it was confirmed that the gas sensor of Example 1 was a highly sensitive potentiometric gas sensor.

(Example 2)
A gas sensor as shown in FIGS. 8A to 8C was produced. Specifically, the gas sensor was produced by the following method.

<Formation of first electrode>
A gold electrode (first electrode 2) having a width of 10 mm, a length of 20 mm, and an average thickness of 60 nm is formed on a silicon wafer with a thermal oxide film having a width of 12 mm, a length of 50 mm, and a thickness of 0.6 mm, and an average thickness of 1 μm. It formed using the vacuum evaporation method.

<Formation of solid electrolyte layer>
Cuprous bromide (solid electrolyte layer 1) having a width of 8 mm, a length of 30 mm, and an average thickness of 200 nm was formed by using an RF magnetron sputtering method so as to cover a part of the first electrode 2.
The conditions of the RF magnetron sputtering method were as follows.
・ RF power: 100W
・ Sputtering gas: Ar
・ Sputtering gas: Flow rate 30sccm
・ Gas pressure: 0.5Pa

<Formation of second electrode>
Further, as shown in FIG. 8A, a gold electrode (second electrode 3) having a width of 10 mm × a length of 20 mm × an average thickness of 60 nm is evacuated so that the gap G with the first electrode 2 has a width of 1 mm. A gas sensor was obtained by using a vapor deposition method.
Here, the gap G is the projected first when the first electrode 2 is projected onto the other surface opposite to one surface of the solid electrolyte layer 1 on which the first electrode 2 is disposed. It means the interval between the end portions of the electrode 2 and the second electrode 3 facing each other.

<Coating with natural rubber>
The obtained gas sensor was immersed in a hexane solution of natural rubber (the concentration of natural rubber was 0.01% by volume) for 1 minute, and the surface was washed with hexane. Then, it dried by the baking process for 30 minutes at 100 degreeC in nitrogen, and fixed the natural rubber layer 5 to the part which the detection object gas in the solid electrolyte layer 1 contacts.

<Evaluation of potential difference change>
Similar to Example 1, nitrogen gas containing ammonia having a concentration of 1 ppm was used to evaluate the change in potential difference using the first electrode 2 as a detection electrode and the second electrode 3 as a reference electrode. The results are shown in FIG.
Due to the migration of copper ions due to the doping of electrons from natural rubber, the potential on the detection electrode side was about 1 mV higher in high purity nitrogen gas. This corresponds to a bias voltage. When the air flow was switched from high-purity nitrogen gas to nitrogen gas containing ammonia having a concentration of 1 ppm, the potential of the detection electrode increased by about 2 mV.
From the above, it was confirmed that the organic substance having a carbon-carbon double bond can be used as a means for promoting the movement of positive charge carriers in the solid electrolyte layer.
Further, it was confirmed that the gas sensor of Example 2 was a highly sensitive potential difference measurement type gas sensor.

(Example 3)
A gas sensor as shown in FIG. 10 was produced. Specifically, the gas sensor was produced by the following method.

<Formation of first electrode and second electrode>
On a silicon wafer with a thermal oxide film having a width of 12 mm × length of 55 mm × thickness of 0.6 mm and an average thickness of 1 μm, two gold electrodes (first electrode 12, width 10 mm × length 25 mm × average thickness 30 nm) And a second electrode 13) were formed using a vacuum deposition method. The two gold electrodes were provided with an interval of 1 mm between the opposing ends.

<Formation of solid electrolyte layer>
A copper layer having a width of 8 mm, a length of 30 mm, and an average thickness of 0.5 μm was formed on the two gold electrodes by using a vacuum deposition method. Subsequently, in literature (Pascal Laquee, Marc Bendahan, Jean-Luc Seguin, Kieu An Ngo, Philippe Knauth, Analytica Chimica Acta, ent. By the method, using the cupric bromide aqueous solution, the copper in the copper layer was changed to cuprous bromide to produce the solid electrolyte layer 11 to obtain a detector.

<Preparation of bias voltage source>
Using a method similar to the above <Formation of first electrode and second electrode> and <Formation of solid electrolyte layer> on a silicon wafer with a thermal oxide film, the width 8 mm × length 20 mm × average thickness 30 nm A copper electrode 15, a cuprous bromide layer (solid electrolyte layer 16) having a width of 8 mm × a length of 15 mm × an average thickness of 0.5 μm, and a silver electrode 17 having a width of 8 mm × length of 15 mm × an average thickness of 30 nm were formed in this order. . The obtained laminated structure was used as a bias voltage source (voltage source 14).

The silver electrode 17 of the voltage source 14 and one gold electrode (second electrode 13) of the detection body were connected to obtain a gas sensor.
An embodiment in which the copper electrode 15 of the voltage source 14 is used as a reference electrode and the other gold electrode (first electrode 12) of the detection body is used as a detection electrode, and the gas sensor is installed in a nitrogen gas flow path. In the same manner as in Example 1, the reaction to ammonia was evaluated by switching the gas source between high-purity nitrogen gas and nitrogen gas containing ammonia having a concentration of 1 ppm while measuring the potential difference between both electrodes. At this time, the voltage by the bias voltage source was −90 ± 3 mV.

  FIG. 11 shows the relationship between the measured potential difference and the change with time. Even when the high purity nitrogen gas is in contact with the solid electrolyte layer 11, the potential of the reference electrode is higher than that of the detection electrode due to the equilibrium of the copper redox reaction occurring at the interface between the cuprous bromide and the copper electrode surface. Was as high as 100 mV. When the air flow was switched from high-purity nitrogen gas to nitrogen gas containing ammonia at a concentration of 1 ppm, the potential of the detection electrode increased, and as a result, the measured potential difference was reduced by about 50 mV.

  As described above, a configuration in which a plurality of electrodes are provided so as not to prevent contact with the atmosphere on the surface of the solid electrolyte layer, and a bias voltage is applied inside the solid electrolyte layer in a direction substantially parallel to the surface in contact with the detection target gas. A highly sensitive potentiometric gas sensor can be obtained even if one of the electrodes in contact with the solid electrolyte layer is a detection electrode and the electrode on the side not connected to the solid electrolyte layer in the bias voltage source is a reference electrode. Was confirmed.

Example 4
Gas sensors as shown in FIGS. 12A to 12C were produced. Specifically, the gas sensor was produced by the following method.

<Formation of first electrode and second electrode>
On a silicon wafer with a thermal oxide film having a width of 12 mm × length of 55 mm × thickness of 0.6 mm and an average thickness of 1 μm, two gold electrodes (first electrode 22, width 10 mm × length 20 mm × average thickness 60 nm) And the second electrode 23) were formed using vacuum deposition. The two gold electrodes were provided with an interval of 1 mm between the opposing ends.

<Formation of solid electrolyte layer>
On the two gold electrodes, cuprous bromide (solid electrolyte layer 21) having a width of 8 mm, a length of 30 mm, and an average thickness of 200 nm was formed using an RF magnetron sputtering method to obtain a device.
The conditions of the RF magnetron sputtering method are the same as those in Example 2.

<Coating with natural rubber>
The obtained device was immersed in a hexane solution of natural rubber (the concentration of natural rubber was 0.01% by volume) for 1 minute. Thereafter, the silicon wafer was dried while the hexane solution was poured down on the surface of the solid electrolyte layer 21 with the long side of the silicon wafer substantially vertical. That is, on the upper side of this drying operation, the amount of natural rubber per unit area on the surface of the solid electrolyte layer 21 is small, and on the lower side, a large state is formed, and the layer 24 covering the solid electrolyte that is the natural rubber layer Obtained. This device was stored in a nitrogen stream at room temperature for 24 hours before use to obtain a gas sensor. In FIG. 12A and FIG. 12C, the amount of natural rubber per unit area in the layer 24 covering the solid electrolyte is shown by color shading. Specifically, the darker the color, the greater the amount of natural rubber per unit area.

<Evaluation of potential difference change>
As in Example 1, the concentration was 1 ppm, using the gold electrode (second electrode 23) on the lower side at the time of drying as the reference electrode and the gold electrode (first electrode 22) on the upper side as the detection electrode. The change in potential difference was evaluated using nitrogen gas containing ammonia. The results are shown in FIG.
Since the amount of electron dope from natural rubber is large on the reference electrode side and small on the detection electrode side, the potential on the detection electrode side was high at 51 ± 1 mV in a high purity nitrogen gas atmosphere. This corresponds to a bias voltage. When the air flow was switched from high-purity nitrogen gas to nitrogen gas containing ammonia having a concentration of 1 ppm, the potential of the detection electrode increased by about 25 mV.
From the above, it was confirmed that the gas sensor of Example 4 was a highly sensitive potentiometric gas sensor.

(Comparative Example 1)
A gas sensor as shown in FIGS. 14A to 14C was produced. Specifically, the gas sensor was produced by the following method.

<Formation of first electrode and second electrode>
On a silicon wafer with a thermal oxide film having a width of 12 mm × length of 55 mm × thickness of 0.6 mm and an average thickness of 1 μm, two gold electrodes (first electrode 32, width 10 mm × length 20 mm × average thickness 60 nm) And the second electrode 33) were formed using a vacuum deposition method. The two gold electrodes were provided with an interval of 1 mm between the opposing ends.

<Formation of solid electrolyte layer>
On the two gold electrodes, cuprous bromide (solid electrolyte layer 31) having a width of 8 mm, a length of 30 mm, and an average thickness of 200 nm was formed using an RF magnetron sputtering method to obtain a device.
The conditions of the RF magnetron sputtering method are the same as those in Example 2.

<Coating with natural rubber>
The obtained device was immersed in a hexane solution of natural rubber (natural rubber concentration is 0.01% by volume) for 1 minute, washed with hexane, and then baked at 100 ° C. for 30 minutes in nitrogen. Went. The natural rubber layer 35 formed on the solid electrolyte layer 31 was uniformly formed on the solid electrolyte layer 31.

<Evaluation of potential difference change>
In the same manner as in Example 1, evaluation was performed using nitrogen gas containing ammonia having a concentration of 1 ppm using one of the two gold electrodes as a reference electrode and the other as a detection electrode. The results are shown in FIG.
In this case, since there is no structural difference between the reference electrode and the detection electrode, there is almost no potential difference between the two electrodes. Even when the air flow is switched from high-purity nitrogen gas to nitrogen gas containing 1 ppm of ammonia, the natural rubber layer 35 does not function as a means for promoting the movement of positive charge carriers, and the potential difference between both electrodes is almost the same. It did not fluctuate.

DESCRIPTION OF SYMBOLS 1 Solid electrolyte layer 2 1st electrode 3 2nd electrode 4 Gas contact part 5 Natural rubber layer 11 Solid electrolyte layer 12 1st electrode 13 2nd electrode 14 Voltage source 15 Copper electrode 16 Solid electrolyte layer 17 Gold electrode 21 Solid electrolyte layer 22 First electrode 23 Second electrode 24 Layer covering solid electrolyte layer 31 Solid electrolyte layer 32 First electrode 33 Second electrode 35 Natural rubber layer 51 Silicon substrate 52 Source electrode 53 Drain electrode 54 Gate Insulating layer 55 Gate electrode 56 First wiring 57 Second wiring 58 Insulating layer α region β region

Claims (16)

A solid electrolyte layer containing positive charge carriers for coordinating the gas to be detected;
A first electrode disposed on a part of one surface of the solid electrolyte layer;
A gas sensor comprising: a second electrode disposed on the other surface of the solid electrolyte layer other than a portion facing the first electrode and in contact with the detection target gas.   The gas sensor according to claim 1, wherein the positive charge carrier is at least one of copper ion and silver ion.   The gas sensor according to claim 1, wherein the positive charge carrier is a copper ion.   The gas sensor according to any one of claims 2 to 3, wherein a material of the second electrode is the same metal as the metal element of the positive charge carrier. A solid electrolyte layer containing positive charge carriers for coordinating the gas to be detected;
A first electrode and a second electrode disposed on a surface opposite to the side in contact with the detection target gas in the solid electrolyte layer;
And a means for accelerating the movement of the positive charge carriers in the surface direction of the solid electrolyte layer and in the direction from the second electrode to the first electrode in the solid electrolyte layer. .   The gas sensor according to claim 5, wherein the means for promoting movement of the positive charge carriers is a voltage source.   The means for accelerating the movement of the positive charge carriers is a layer that is disposed on at least a part of the surface of the solid electrolyte layer on the side in contact with the gas to be detected and covers the solid electrolyte layer. The gas sensor described.   The gas sensor according to claim 7, wherein the layer covering the solid electrolyte layer is a layer containing a substance capable of coordinating with the positive charge carriers and transmitting the detection target gas.   The gas sensor according to claim 8, wherein the substance capable of coordinating with the positive charge carrier is an organic substance having a carbon-carbon double bond.   The gas sensor according to claim 9, wherein the organic substance having a carbon-carbon double bond is any one of polyisoprene rubber, natural rubber, and polybutadiene rubber.   The gas sensor according to claim 5, wherein the positive charge carrier is at least one of copper ion and silver ion.   The gas sensor according to claim 5, wherein the positive charge carrier is a copper ion.   The gas sensor according to any one of claims 1 to 12, wherein a material of the solid electrolyte layer is any one of cuprous bromide, cuprous sulfide, silver sulfide, silver iodide, and silver rubidium iodide.   The gas sensor according to any one of claims 1 to 13, wherein a material of the solid electrolyte layer is cuprous bromide. A gas sensor according to any one of claims 1 to 14,
A sensor device connected to the first electrode of the gas sensor to detect a change in potential difference of the gas sensor;   The sensor device according to claim 15, wherein the means for detecting a change in potential difference of the gas sensor is a field effect transistor.